1. Field of the Invention
This invention relates to a cutter drum assembly for use on a boring type mining machine and, more particularly to a cutter drum having extensible end drums for expanding the cutting width of the cutter drum to dislodge solid material left uncut by the rotor cutter arms from a mine face at the mine roof and floor.
2. Description of the Prior Art
Boring machines for underground mining operations are well known in the art as illustrated in U.S. Pat. Nos. 3,041,054; 3,309,143; 3,325,218; 3,339,982; 3,515,217; 4,339,153; and 4,889,392. Typically, these types of boring machines utilize parallel interlaced rotor arms having cutting elements which cut a generally oval-shaped entry in the mine. Cutter chains or continuous cutter drums are utilized at the roof and floor levels to trim or eliminate cusps left in place because they are out of the cutting paths of the rotor arms. The cutter chain or drum at the mine floor is also used to increase the width of the cut in the mine entry.
To facilitate tramming of the machine into and out of position opposite of the mine face, the lower cutter chain or drum is retracted out of contact with the mine sidewalls and raised out of contact with the mine floor. The upper cutter chain or drum is lowered out of contact with the mine roof.
To increase the width of the cut at the mine floor beyond the cutting path of the rotor arms, it is necessary to extend the width of the lower cutter drum once its lowered into position on the mine floor at the base of the mine face. U.S. Pat. Nos. 3,730,593, 3,774,969, and 4,076,316 disclose the concept of extending the length of a cutter drum assembly on continuous mining machines.
U.S. Pat. Nos. 3,730,593 and 3,774,969 each disclose a continuous mining machine having a cutter drum assembly rotatably mounted on a forwardly extending boom member. A plurality of cutter bits extend outwardly from the drum member. The drum member includes intermediate drum sections and a pair of end drum sections. The intermediate and end drum sections are telescopically mounted to extend the length of the drum assembly beyond the width of the machine. Extension of the end drum sections is accomplished by lateral movement of a boom member having arm members which rotatably support end drum sections. The lateral movement is generated by hydraulic piston cylinder assemblies that exert lateral pressure on the boom arms.
U.S. Pat. No. 4,076,316 also discloses a continuous mining machine having a forwardly extending boom assembly pivotally secured to the frame of the mining machine. The boom assembly includes a pair of parallel forwardly extending arm members that are pivotally connected to the mining machine body portion. A pair of parallel support members are movably secured to and extend laterally from the respective arm members. A cutter drum is rotatably supported at the forward end portions of the support members. A pair of cylinder assemblies are secured to respective arm members and each includes an extensible cylinder rod secured to a support member. Actuating the cylinder assemblies extends the end drum sections laterally away from an intermediate drum section. The end drum sections are independently extendable to increase gathering efficiency.
The known prior art drum extension mechanisms utilize hydraulic cylinder assemblies to both initially extend the cutter drum end portions and maintain them in an extended position. The continuous pressure exerted on the hydraulic mechanisms accelerates wear of the seal components necessitating increased maintenance demands.
In dual rotor boring machines, a lower cutter drum assembly trims material at the mine floor left uncut by the rotor arms. Typically, the cutter drum includes a center or intermediate drum section and a pair of end drum sections separated from the intermediate drum section by gear cases. The gear cases rotatably support the respective cutter drum sections.
In a dual rotor assembly, each gear case is positioned below and centered on a rotor axis. With this arrangement, when the end drums are extended to increase the length of the lower cutter drum to increase the width of cut, gaps are formed in the cutting paths between the extended end drums and the rotor arms. This leaves uncut material or cusps projecting upwardly from the mine floor at the mine face.
An alternative prior art arrangement includes each drum section having a fixed portion and an outer extensible portion. The outer portions are extended from the end drum fixed portions to increase the width of cut. However, this requires that in a retracted position the cutting elements on the end drum outer portions interlace with the cutting elements on the end drum fixed portions. This arrangement complicates the structure of the end drum section because of the limited length of the end drum section.
While it is known to extend the length of a cutter drum assembly on a continuous mining machine, there is a need for an extensible lower cutter drum assembly on a boring type mining machine that reduces the wear on the hydraulic seal components of the extension device to extend the operating life of the seal components. Furthermore, the lower cutter drum assembly must be operable in both retracted and extended positions to combine with the rotor arms in completely dislodging the mine material at the mine floor as the machine advances the mine face.